on a Lenovo ThinkCentre M77, running 6.4-stable (amd64), I get
bge0: APE event 0x00020510 send timed out
bge0: APE event 0x00010510 send timed out
The bge0 is a Broadcom BCM5761 A1 (0x5761100), APE firmware DASH 188.8.131.52.
After plugging in a cable directly connected to another machine,
auto-assigning IPv6 addresses and ping6ing back and forth,
it looks like the bge0 sends out frames but never receives any.
Up to OpenBSD 6.1 this (and a lot more) worked.